The TPA3100D2 is a 20-W (per channel) efficient, Class-D audio power amplifier for driving bridged-tied stereo speakers. The TPA3100D2 can drive stereo speakers as low as 4 . The high efficiency of the TPA3100D2, 92%, eliminates the need for an external heat sink when playing music. The gain of the amplifier is controlled by two gain select pins. The gain selections are 20, 26, 32, 36 dB.